1. Field of the Invention
This invention relates to the delivery of vaccines and more particularly it concerns novel methods and apparatus for packaging and dispensing vaccines of the type which are administered by injection through a needle.
2. Description of the Prior Art
In general, vaccines, after being harvested from a culture tank, are clarified, diluted, subdivided into vials or ampules and then lyophilized. When lyophilized the vaccine may be kept for extended periods of time at low temperature, i.e., 4.degree. C. with losses substantially below those encountered in aqueous vaccines. The lyophilized vaccine is supplied with diluent and occasionally with disposable syringes. In this latter case, the syringe itself may carry the diluent liquid which is injected into the vaccine ampule or vial just prior to administration. The diluent dissolves or suspends the vaccine and the vaccine is withdrawn back into the syringe for administration by injection.
The above described technique for vaccine delivery suffers from a number of drawbacks. Firstly, the lyophilization process results in a high loss of titer which in turn requires a high overcharge of vaccine. Further, storage results in an additional loss of titer which must be compensated for. In addition, there is a relatively high cost for the lyophilization operation itself. The cost of the conventional syringes is quite high. There is also the potential for incomplete suspension of the vaccine during rehydration and the possibility for contamination and additionally the technique is costly of the valuable time of the medical personnel doing the injections.